In this study, we describe a synthesized peptide with C-terminally amidated, GAPKGCWTKSYPPKPCS-amide that contains a disulphide loop between Cys6 and Cys16 that is consistent with a Bowman–Birk type protease inhibitor, from the skin secretion of the frog Pelophylax nigromaculatus. The precursor was obtained from the Pelophylax nigromaculatus skin secretion by employing molecular cloning. The corresponding mature peptide, namely QUB-1804, was identified by bioinformatics approach from this cloned biosynthetic precursor-encoding cDNA sequence. Subsequently, the chemically-synthesised replicate was subjected to a series of bioassays. It was found that QUB-1804 is a Bowman-Birk-type protease inhibitor which belongs to ranacyclin family. It has respectively trypsin inhibitory activity with Ki value of 0.373 μM. But QUB-1804 does not possess significant antimicrobial activity on three model micro-organisms: Gram-positive bacterium (S. aureus), Gram-negative bacterium (E. coli) and an opportunistic yeast bacterium (C. albicans). Additionally, this peptide failed to inhibit the proliferation of cancer cell this peptide towards PC-3, H157, U251MG and MCF-7 cancer cell lines at the challenge concentration of 10-5 M. Meanwhile, this peptide showed, there is no significant haemolysis when the concentration is lower than 256 μM. These data provide evidence that this peptide properly could be a novel promising trypsin inhibitory candidate.